<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.7.10/dist/vue.js"></script>
    <style>
        .one {
          width: 100px;
          height: 100px;
          background-color: yellow;
        }
        .two {
          width: 100px;
          height: 100px;
          background-color: hotpink;
        }
        .three {
          width: 100px;
          height: 100px;
          background-color: red;
        }
      </style>
</head>
<body>
    <div id="app">
      <!--  元素强制绑定一个class属性,我们通过改变data中的class数据来控制视图更新 --> 
        <div :class = "className"></div>
    </div>
    <script>
        const vm = new Vue({
            el:"#app",
            data(){
                return {
                    className:"two"
                    }
                }
            }
        )
    </script>
</body>
</html>